The music compressed in MP3 (MPEG Audio Layer-3) format becomes more and more popular. MP3 is a data compression/decompression standard subordinate to MPEG (movie picture experts group) by which the audio can be compressed to 1/10 or 1/12 storage amount. For example, the MP3 audio CD can store about 100 songs of ordinary playing time. However, the MP3 audio CD is generally reproduced by computer rather than CD player. Therefore, the reproducing apparatus and method for MP3 music are under extensive research for easier use.
FIG. 1 shows the system block according to a prior art data compression method 100a. The prior art data compression method 100a comprises steps of reading two adjacent data in the content table of compact disk, which represent the absolute playing time of compact disk and are stored in the content table in a first carry format; subtracting the two adjacent data in the content table to obtain a relative data representing the relative playing time of the compact disk; converting the relative data to a plurality of values in a second carry format; storing the non-zero ones of the plurality of values and indicating the byte number of non-zero values by a flag.
However, the above mentioned prior art has following drawbacks:
1. The recording and reproducing operations can not be performed simultaneously due to lack of real-time decompressing step. PA1 2. The data is read from compact disk and can not be read from other source such as computer network or audio means. PA1 3. The compressed data is stored in the volatile data memory such as RAM of the micro-controller, the data preservation is limited by power.
FIG. 2 shows the system block diagram of another prior art wherein a hand-held and flash memory based voice recording/reproducing device for language learning is disclosed. The hand-held voice recording/reproducing device comprises a CPU 1a, an input unit 2a connected to the CPU 1a, a liquid crystal display unit 3a, a system memory 4a, a database memory 5a, an audio output 6a, a first playback key, a DSP unit 7a, and a A/D converter 8a. The user input the command thereof through the input unit 2a such that the CPU 1a reads an object text data from the database memory 5a. Afterward, the object text data is displayed on the liquid crystal display unit 3a. The first playback key is pressed to generate an object voice data reading signal by which an object voice data is read and processed by the A/D DSP unit 7a and the converter 8a, and then enhanced through the audio output 6a. The prior art hand-held voice recording/reproducing device is characterized in that the A/D converter 8a is further connected to a microphone 9a, and the CPU 1a is electrically connected to a separable flash memory 13a, a recording key and a second playback key. The recording key provides a recording control signal to the CPU 1a such that the microphone 9a receives the analog voice data corresponding to the object voice data. The analog voice data is converted to a digital voice data and compressed by the DSP unit 7a, and then stored in the flash memory 13a. The second playback key provides a voice reading signal to the CPU 1a such that the voice data stored in the flash memory 13a is decompressed by the DSP unit 7a and then converted to an audio voice. The audio voice is sent to the audio output 6a for enhancing.
However, the above-mentioned voice recording/reproducing device for language learning has following drawbacks:
1. The power supply 14 thereof has no long-term primary and secondary power control module. Therefore, the above-mentioned voice recording/reproducing device has only primary power supply for liquid crystal display and does not have secondary power supply for memory.
2. The flash memory 13a used in the above-mentioned voice recording/ reproducing device is costly and the device has not the ability to charge the primary and secondary power supply when using the flash memory.
3. The voice signal can not be transmitted through the path from the CPU 1a to the flash memory 13a.
4. The system memory 4a and the database memory 5a are provided for read only data, thus being not rewritable. It is not suitable for the application of real-time compressing and decompressing voice data.
5. The input unit 2a does not have expansion control code unit, the mode of input means is limited.
6. The above-mentioned voice recording/reproducing device uses liquid crystal display unit 3a only, and does not use other display device such as plasma display.
It is the object of the present invention to provide a real-time compressing and decompressing apparatus for recording and reproducing multi-soundtrack voice data, which can overcome the above mentioned problems.
To achieve the object, the present invention provides a real-time compressing and decompressing apparatus for recording and reproducing multi-soundtrack voice data. The real-time compressing and decompressing apparatus comprises a real-time decompressing module for reproducing digital voice; a pre-module for real-time compressing digital voice; a long-term primary and secondary power control module; a controllable working-frequency adjusting module; a linking module for supplying power; and a digital voice memory module. Therefore, the digital voice is not distorted, the voice data is read directly from computer network and audio input unit and real-time compressed to store in memory. Moreover, the decompression operation is performed simultaneously with the compression operation to real-time playback voice data. The data can be sustained for long time. The present invention provides primary power for main operation and secondary power for memory storage, and uses SDRAM in place of flash memory to reduce cost.
The various objects and advantages of the present invention will be more readily understood from the following detailed description when read in conjunction with the appended drawing, in which: